I mounted a floodlight on the radar mast for my J/109. It's a fairly bright LED model that draws almost no current. I usually leave it on when we are at the dock or on the mooring while cruising as it makes it easy to find the boat in a mooring field. The "cocktail light" is bright enough to perform an appendectomy on someone in the cockpit.

Rather than moving the stern light to the radar mast for visibility, you are better off putting a tri-color LED at the top of the mast. You get better all round visibility from others. I have the deck lights and tri-color on a DPDT switch. You aren't supposed to have both illuminated at the same time. In shore, the deck level lights are better for visibility. Off shore the masthead is better.

Attached is a picture of the radar mast on my J/109. It is easily removable for racing. This was taken last summer during an off-shore doublehanded race. You can see it holds everything including the loudhailer speaker (for the fog horn), the radar reflector, the deck light and the class flag. I snapped this picture of my crew member Eric on the New England Solo-Twin regatta.



ps - nice looking asym there. Where did it come from?